FIELD TESTING OF A NONDESTRUCTIVE PORTABLE PERMEABILITY INDICATOR FOR CONCRETE

A portable, battery powered device has been developed which affords a nondestructive measure of permeability of a concrete surface. The device creates a vacuum of approximately -25 in. of Hg at the concrete surface and measures the rate of air flow (in mL/min) using a mass flowmeter. Reusable closed cell foam gaskets are used to insure a tight seal to rough surfaces. A detachable vacuum plate can be used to obtain measurements on vertical or overhead surfaces. Readings can be obtained at the rate of approximately one per minute, allowing a large amount of information to be developed at close intervals across a given concrete member. Field trials of the device were carried out on bridges in the states of Pennsylvania and Texas. Bridge elements tested included decks, support beams, and pier caps. It was possible to test a 40 ft long span in one lane over a period of about 2 hours using a test grid established on 3 ft centers. Support elements can also be tested, although in many cases scaffolding, man lifts, or other devices may be needed to access elements beyond reach. In addition to the nondestructive testing, cores were obtained from a number of locations on each test structure and subsequently tested in the laboratory for air permeability. Relationships between field measurements and actual air permeabilities were generally good. Potential applications of the device could include such activities as: 1) determination of relative permeability of concrete during rehabilitation surveys, 2) verification that low permeability has been established for special concrete overlays, and 3) establishing general quality of concrete in routine construction or in cases where questions have arisen.